1. Field of the Invention
The present invention relates to a liquid ejection head configured to eject liquid, and a recording apparatus including the liquid ejection head.
2. Description of the Related Art
Among liquid ejection heads, for example, an ink-jet recording head for use in an ink-jet recording apparatus includes a recording element substrate having ink ejection orifices formed therein so as to allow ink droplets to be ejected therefrom, and a support member configured to support the recording element substrate. On the recording element substrate, recording elements for generating ejection energy are arranged so as to correspond to the ink ejection orifices. As the recording elements, heating resistance elements such as heaters are employed. In addition, in the support member, an ink supply path from which ink is supplied to the recording element substrate is formed.
In the above-mentioned ink-jet recording head, as the number of the recording elements arranged on the recording element substrate is increased and a recording width capable of performing recording on a recording medium is increased, recording can be performed at higher speed. Accordingly, the number of the recording elements and the recording width are being increased. In recent years, in order to realize recording at higher speed with higher image quality, attention is paid on a liquid ejection head in which a plurality of recording element substrates are arranged in series over a length equal to or larger than a width of the recording medium (hereinafter referred to as a line head).
As a configuration of the line head, there is a configuration in which a plurality of the ink-jet recording heads are connected together or a configuration in which the support member is elongated and a plurality of the recording element substrates are arrayed on the support member. In the line head having the latter configuration, when the recording element substrates each having a rectangular shape in plan view are arranged in series so that rows of the ink ejection orifices, from which the same kind of ink is ejected, are arranged in a straight line across all of the recording element substrates, a plurality of boundaries are formed between the adjacent recording element substrates. As a result, due to an influence of a manufacture error of each of the recording element substrates, it is difficult to match the interval between the two ink ejection orifices adjacent to each other with each of the boundaries therebetween to an interval between the ink ejection orifices formed in each of the recording element substrates. Accordingly, intervals between ink droplets which are ejected onto a recording medium from the rows of the ejection orifices for the same kind of ink of all of the recording element substrates may not be equalized. In order to solve this problem, hitherto, there has been proposed a line head having a configuration in which the recording element substrates each having a rectangular shape are arranged in a zigzag pattern, and also arranged so that positions of longitudinal end portions of the respective recording element substrates overlap each other when viewed from a direction perpendicular to the arranging direction of the recording element substrates (this direction corresponds to a conveying direction of the recording medium, and is hereinafter referred to as a “main scanning direction”.). In the configuration employing zigzag arrangement, as compared to the above-mentioned example, it is easy to equalize the intervals between the ink droplets, which are ejected onto the recording medium from the rows of the ejection orifices for the same kind of ink of all the recording element substrates, when viewed from the main scanning direction. Thus, it is possible to prevent degradation of image quality at the positions where the longitudinal end portions of the respective recording element substrates overlap each other.
In addition, as a configuration made to achieve downsizing as compared to the above-mentioned line head employing the zigzag arrangement, the following configuration (Japanese Patent No. 4539549) has been proposed. Specifically, the outer shape of the recording element substrate exhibits a parallelogram in plan view. Further, when a plurality of the recording element substrates are arrayed on the support member having a long length, the recording element substrates are placed so that a pair of opposing sides of the recording element substrates are inclined with respect to the arraying direction, and the inclined sides of the respective recording element substrates are arranged in intimate contact with each other. In particular, in this configuration, under a state in which the inclined sides of the respective recording element substrates are arranged in intimate contact with each other, the recording element substrates are placed from one longitudinal end side to another longitudinal end side of the support member so as to be staggered in the main scanning direction. This configuration can equalize the intervals between the ink droplets, which are ejected onto a recording medium from the rows of the ejection orifices for the same kind of ink of all the recording element substrates, when viewed from the main scanning direction. In this configuration, unlike the above-mentioned line head employing the zigzag arrangement, it is unnecessary to stagger the adjacent recording element substrates in the main scanning direction by a distance or more corresponding to the width of the recording element substrate in the main scanning direction. Accordingly, this configuration can be downsized as compared to the line head employing the zigzag arrangement.
Further, in order to achieve easy manufacture in addition to the downsizing of the line head, there has been proposed a configuration in which a recording element substrate having a rectangular shape in plan view is mounted on a carrier so as to form a recording element module, and the recording element modules are arrayed in series on a support member (US 2013/0083120).
When manufacturing the line head, recording element members, such as the recording element module and the recording element substrate, are fixed by bonding on the support member using an adhesive. In a case where a thermally curable adhesive is employed as the adhesive, the recording element members are arranged on the support member through the thermally curable adhesive, and then a heating process of heating the entire line head so as to cure the adhesive is performed. In general, different materials are used for the recording element members and the support member, and the recording element members and the support member have different coefficients of linear expansion. Accordingly, when the support member and the recording element members, which are fixed by bonding to each other in the heating process, return from a high-temperature state caused by the heating process to a room-temperature state, a difference in thermal shrinkage amount occurs between the support member and the recording element members. Due to the difference in thermal shrinkage amount, stress acts on the cured thermally curable adhesive between the support member and the recording element members (hereinafter referred to as an adhesion region).
Here, when defining an XY orthogonal coordinate system on a surface of the support member configured to support the recording element members, the above-mentioned stress can be represented by forces generated in opposite directions with a center line of the adhesion region (line passing through a center of gravity of the adhesion region) therebetween in each of the X-axis direction and the Y-axis direction of the coordinate system. The forces generated in the opposite directions with the center line of the adhesion region therebetween may not act symmetrically with respect to the center line of the adhesion region depending on the shape of the adhesion region. In this case, when the temperature of the line head is returned to room temperature after the line head is subjected to the heating process as described above, the adhesion region is turned. For example, as illustrated in FIG. 1C1, in a case where a recording element substrate 4 having a parallelogram shape in plan view is fixed on a support member 2 through a liquid chamber member 3, when the outer shape of the liquid chamber member 3 exhibits a parallelogram similarly to that of the recording element substrate 4, an adhesion region between the support member 2 and the liquid chamber member 3 also exhibits substantially a parallelogram. In a case where the adhesion region exhibits a parallelogram in this manner, as illustrated in FIG. 1C1, forces generated in opposite directions with a center line Lx of the liquid chamber member 3 therebetween do not act symmetrically with respect to the center line Lx. In addition, forces generated in opposite directions with a center line Ly of the liquid chamber member 3 therebetween do not also act symmetrically with respect to the center line Ly. Accordingly, on two sides of the liquid chamber member 3 opposing to each other in each of the X-axis direction and the Y-axis direction, there are portions in which the forces do not cancel each other out (see the solid arrows of FIG. 1C1), with the result that turning of the liquid chamber member 3 may be caused.
As described above, when the turning of the adhesion region is caused, the position of the recording element substrate fixed on the adhesion region is shifted in association with the turning. Therefore, positions of the ink ejection orifices of the recording element substrate are displaced from desired positions, and positions at which ink droplets ejected from the ink ejection orifices land the recording medium (recording positions) are also shifted from desired positions. As a result, quality of the image recorded with the ink is degraded.